Lipid pattern and Na+−K+-dependent adenosine triphosphatase activity in the salt gland of duck before and after adaptation to hypertonic saline

Summary Ducks (Anas platyrhynchos) were fed hypertonic saline for eight days, resulting in an activation and hypertrophy of the salt gland. The Na⁺–K⁺-dependent adenosine triphosphatase, an enzyme generally assumed to be part of the active Na transport system, increased its specific activity by about 200% during this activation. Sulfatides, the major glycolipids of the salt gland, increased their concentration to the same extent. Cholesterol, cerebrosides, and six phospholipid classes showed an increase of 20–80%.A preliminary report on this work was given at the Second International Meeting of the International Society for Neurochemistry, Milan, September 1–5, 1969, and at the XIIIth International Conference on the Biochemistry of Lipids, Athens, September 7–12, 1969.     

Microdensitometer system for microradiography

Summary A microdensitometer system for point measurements in areas down to a few square micrometers is described. The detector system is connected to an integrating digital voltmeter, constituting a very sensitive system. The digital output signals and a digital identification are registered on a recorder and on a tape punch, thus facilitating computer analysis.The precision of the equipment varied from 1.1 per cent, for low signal levels, to 0.3 percent for the highest signal levels. Stray light, the only important source of systematic errors, was found to influence the output signal level. Concerning determinations of the densities, however, a variation of the order of 1 per cent was only obtained for small areas with densities differing from that of the background.     

Changes in the anatomical structure of the shoot apex ofSenecio vulgaris L. during ontogenis in relation to the formation of leaves and inflorescence

An investigation was made of the anatomical structure of the shoot apex ofSenecio vulgaris L. a photoperiodically neutral plant, and compared with the formation of successive leaf primordia along the axis up to the initiation of the terminal inflorescence. In the shoot apex of a germinating plant a central zone can first be distinguished from the peripheral zone which is composed of small and intensely stained cells. Later, a rib meristem appears. At the time of the initiation of the middle (the largest) leaves, the shoot apex has a distinct small central zone and a well developed peripheral zone and rib meristem. Between these zones there is a group of cells dividing in all directions, the subcentral zone. At the time of initiation of the last leaves, the central zone extends to the flanks and gradually ceases to be distinguishable. At the same time, the subcentral zone increases in size. This is caused first by cell division and later, with the initiation of the last, most reduced leaves, by enlargement of the cells. Vacuolization in the inner part of the apex and the arrangement of the superficial cells in rows parallel to the surface of the apex, is a preparatory step to the initiation of the inflorescence.     

Why do males of the dance flyEmpis borealis refuse to mate? The importance of female age and size

Empis borealisfemales form swarms, and males carrying a nuptial gift come to swarms to mate. Males either mated with one of the females (accepted swarms) or left swarms without mating (refused swarms). Males mated with the younger (low wing-wear) and relatively larger females in accepted swarms. They seemed to be able to judge the relative size of the females but to ignore their absolute size. Visiting males stayed shorter in accepted swarms as female size variation increased. This probably reflects their greater ease in choosing a mate among females of relatively different sizes. Females in accepted swarms tended to be larger and to have less worn wings than females in rejected swarms.     

洪湖野菰及其化学成分分析

野菰(Zizania latifolia)是湖北省洪湖中优势水生维管束植物,其群落占全湖355平方公里面积的127平方公里。茎和叶的年生物量为4379克鲜重/平方米,全湖总年产量121700吨干重,目前未被利用。野菰各器官的蛋白质和氨基酸含量分别以百分干重表示:根,7.0和4.76;根状茎,11.3和8.85;茎,9.5和7.15;嫩茎梢,22.4和16.53;叶,16.8和14.61。500克干叶的必需氨基酸含量接近100克干重草鱼幼鱼背肌的必需氨基酸含量。脂肪:叶中3.4～4.2,茎中2.2;粗纤维:叶中26.8～28,茎中24.2;灰分:叶中10.0,茎中5.8。菰茎含可溶性糖类30％以上,其中葡萄糖,果糖、蔗糖和麦芽糖是主要成分。结果表明野菰是一种优质饲料。     

Qualitative importance of the microbial loop and plankton community structure in a eutrophic lake during a bloom of cyanobacteria

Plankton community structure and major pools and fluxes of carbon were observed before and after culmination of a bloom of cyanobacteria in eutrophic Frederiksborg Slotssø, Denmark. Biomass changes of heterotrophic nanoflagellates, ciliates, microzooplankton (50 to 140 μm), and macrozooplankton (larger than 140 μm) were compared to phytoplankton and bacterial production as well as micro- and macrozooplankton ingestion rates of phytoplankton and bacteria. The carbon budget was used as a means to examine causal relationships in the plankton community. Phytoplankton biomass decreased and algae smaller than 20 μm replacedAphanizomenon after the culmination of cyanobacteria. Bacterial net production peaked shortly after the culmination of the bloom (510 μg C liter^?1 d^?1 and decreased thereafter to a level of approximately 124 μg C liter^?1 d^?1. Phytoplankton extracellular release of organic carbon accounted for only 4–9% of bacterial carbon demand. Cyclopoid copepods and small-sized cladocerans started to grow after the culmination, but food limitation probably controlled the biomass after the collapse of the bloom. Grazing of micro- and macrozooplankton were estimated from in situ experiments using labeled bacteria and algae. Macrozooplankton grazed 22% of bacterial net production during the bloom and 86% after the bloom, while microzooplankton (nauplii, rotifers and ciliates larger than 50 μm) ingested low amounts of bacteria and removed 10–16% of bacterial carbon. Both macro-and microzooplankton grazed algae smaller than 20 μm, although they did not control algal biomass. From calculated clearance rates it was found that heterotrophic nanoflagellates (40–440 ml^?1) grazed 3–4% of the bacterial production, while ciliates smaller than 50 μm removed 19–39% of bacterial production, supporting the idea that ciliates are an important link between bacteria and higher trophic levels. During and after the bloom ofAphanizomenon, major fluxes of carbon between bacteria, ciliates and crustaceans were observed, and heterotrophic nanoflagellates played a minor role in the pelagic food web.     

双胸蚓纤溶酶的纯化及性质

 用硫酸铵分段盐析、超滤膜分级分离及DEAE-纤维素、Sephadex A-25和Sephadex G-50三种柱层析方法从双胸蚓组织的粗提取液中分离纯化出一种纤溶酶,分子量为29kD,由一条肽链组成。此晦具有强烈的溶解纤维蛋白的作用,对家兎实验性血凝块也具有明显的溶解作用。此酶的最适pH为8.0,在pH7.6～8.4之间活力相差不到2％;酶在PH4.7—11.0范围内稳定;酶作用的最适温度为57℃;此酶热稳定性较好,于25～50℃保温3小时,酶活力基本不变,60℃时,活力保留65％。金属离子Na~(+)、K~(+)、Mg~(2+)等可提高此酶的活力,而Hg~(2+)、Ca~(2+)等金属离子对此酶有不同程度的抑制作用。     

Characterization of an in vitro system of human renal papillary collecting duct cells

Summary We have developed an in vitro model of human papillary collecting duct cells isolated from cadaver kidneys using methods similar to those we previously reported for the isolation of human proximal tubule cells. To date we have isolated papillary collecting duct cells from 100 normal human kidneys. Papillae were dissected and digested in Cellgro containing 400 U/ml collagenase. Cells were plated on fibronectin-coated culture flasks at a density of 10⁴ live cells/ml in Cellgro supplemented with insulin and 10% fetal bovine serum. Confluent monolayers, which were able to withstand 600 mOsm for 8 h, were obtained within 10 to 15 d. Cells of primary isolates and first passages exhibited epithelial cell ultrastructure including cell junctions, microvilli, and cilia. A dark-brown reaction product was observed in these cells when stained by the immunoperoxidase method with peroxidase-labeled peanut lectin (Arachis hypogaea), which binds specifically to human distal tubule and collecting duct cells. These cells were negative for Factor-VIII (a marker for endothelial cells) and γ-glutamyltransferase (a marker for proximal tubule cells). High activities of the glycolytic enzyme pyruvate kinase and arginine vasopressin-stimulated cAMP production in these cells are consistent with a distal nephron origin. The results indicate that human collecting duct cells can be isolated and cultured to provide an in vitro system to probe pathogenetic mechanisms of potential nephrotoxins. Part of this work was presented at a Symposium of the Center for Alternatives to Animal Testing, April 4–5, 1989, Johns Hopkins Medical Institutions, Baltimore, MD 21205. This work was supported in part by grants R01-AI24179, PO1-A804393 for the Public Health Service, U.S. Department of Health and Human Services, and by a grant from the National Kidney Foundation, Baltimore, MD affiliate.